In batteries, as lithium-ion cells continue to increase in energy density, there is a corresponding increase in the total release of energy and temperature of the material released during catastrophic failure. The likelihood of cascaded, catastrophic cell failures in multi-cell packs when a single cell experiences catastrophic failure also increases. That is, as lithium-ion batteries become higher and higher in energy density, the likelihood of cell swell also increases. Cell swell, which can be referred to as battery bloating or swollen batteries, occurs in lithium-ion cells, and the cell swell includes the lithium-ion cells physically bulging, typically from a midsection of the cells. All battery packs, with lithium-ion cells, are designed with space to accommodate the normal end of life cell swell. Exposure to extreme conditions (e.g., high temperatures, abusive conditions, extended cycle life, inappropriate charge termination) may result in severe cell swell. Users perceive swollen cell packs as potential safety issues. Also, the swollen cells can also cause permanent product damage. Packing more cells and higher energy cells into products requires better techniques to take batteries out of service before users take them to a critical cell swell point which can result in perceived safety concern (bulging) and possible product damage (e.g. cracked displays, housings, etc.).
Accordingly, there is a need for a method and apparatus to detect and manage battery pack cell swell.
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The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.